In recent years, idling-stop vehicles have been commercialized in order to reduce the consumption of fuel and exhaust gasses. Idling-stop vehicles are vehicles that automatically stop (idling-stop) an engine upon detection of a stop operation of a vehicle due to a wait for a traffic light or the like, and automatically restart the engine upon detection of a starting operation of the vehicle thereafter.
In such idling-stop vehicles, a voltage of a battery is temporarily decreased because a high electric current flows into a starter motor for starting an engine at the restarting of the engine after being idling-stopped. In association with this, a voltage supplied to a load such as an electronic device and the like, connected to the battery, other than the starter motor is also temporarily decreased. Accordingly, there is a possibility that the supplied voltage will deviate from a voltage range needed for operations, depending on a load, leading to a temporarily abnormal operation. This poses a possibility that an operation not intended by a driver will be performed. For example, a car navigation system or an audio system may be reset, or the audio system may skip.
Accordingly, such idling-stop vehicles are provided with a power source circuit between a battery and a load so that a necessary voltage can be kept supplied to the load even if the voltage of the battery is temporarily decreased.
For example, a power source circuit for boosting and outputting a voltage of a battery to a load by continuously turning off a bypass switch and operating a booster circuit at a restarting of an engine after being idling-stopped, and for outputting the voltage of the battery to the load via the bypass switch by continuously turning on the bypass switch and suspending the booster circuit at normal times other than the restarting of the engine, is proposed as an existing power source circuit (for example, see Patent Document 1).
This makes it possible to maintain a necessary power supplied to the load even when the voltage of the battery is temporarily decreased at the restarting of the engine after being idling-stopped. Moreover, the voltage of the battery is output to the load without being decreased by an element within the booster circuit at normal times other the restarting of the engine after being idling-stopped, whereby it becomes possible to maintain the necessary power supplied to the load.